Priority is claimed on Japanese Patent Application No. 2007-61464, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a thread cutting insert that is held on a tool main body of a detachable insert type cutting tool, for performing thread cutting on a workpiece.
2. Description of Related Art
As this type of thread cutting insert, in the following Patent Documents 1 to 4 for example, there have been proposed various kinds of thread cutting inserts in which, in each corner section of a triangular face of a triangular flat plate shaped insert main body, there is formed a cutting edge section that forms a convex V shape when seen from the direction facing the triangular face, and the convex V shape face of this cutting edge section serves as a rake face, on the side ridgelines of which there are formed a pair of thread cutting edges that form a convex V shape corresponding to the cross-sectional shape of the thread to be cut. Also, the inventors of the present invention proposed to achieve an improvement in chip processing with such a thread cutting insert disclosed in Patent Document 5 below.
(1) Patent Document 1: Japanese Unexamined Patent Application, First Publication No. H08-257837
(2) Patent Document 2: Japanese Unexamined Patent Application, First Publication No. H08-294804
(3) Patent Document 3: Published Japanese Translation No. H09-502396 of PCT International Publication
(4) Patent Document 4: Published Japanese Translation No. 2001-514089 of PCT International Publication
(5) Patent Document 5: Japanese Unexamined Patent Application, First Publication No. 2006-123041
However, in the conventional thread cutting inserts disclosed in these Patent Documents 1 to 5, even with a negative type insert, the flank face of which extends in parallel with the thickness direction of the insert main body, the thread cutting edge is formed only on a convex V shape face of a cutting edge section on the side of one of a pair of front-back triangular faces of the triangular flat plate shaped insert main body. Accordingly, with a generic negative type flat plate shaped insert, while a cutting edge formed in a corner section that is common for both of the front and back faces can be used, the number of corner sections that are available for use becomes half. As a result, in this type of thread cutting insert in which the portion to be used as a cutting edge is already small enough, even if the insert main body is formed from a super hard alloy or the like, effective use of the insert main body is hardly achieved.
The present invention takes the above circumstances into consideration, and its object is to provide an economical thread cutting insert that increases the number of thread cutting edges that are available for use with a single insert main body to achieve effective use of the insert main body.